Tool Tip Research Articles

A semi-autonomous robot control based on bone layer transition detection for a safe pedicle tapping.

Automatic robotic platforms for robot-aided spinal surgery are mostly employed for drilling the pedicle screw path and do not adapt the tool rotational speed depending on the variation of the bone density. This feature is highly desirable in control strategies for robot-aided pedicle tapping, which may result in a poor quality thread if the surgical tool speed is not adequately tuned depending on the bone density to be threaded. Therefore, the objective of this paper is to propose a novel semi-autonomous control for robot-aided pedicle tapping that is able to (i) identify the bone layer transition, (ii) adapt the tool velocity depending on the detected bone layer density and (iii) stop the tool tip before propulsion of the bone boundaries. The proposed semi-autonomous control for pedicle tapping consists of: (i) a hybrid position/force control loop that allows the surgeon to move the surgical tool along a pre-planned axis and (ii) a velocity control loop that allows him/her to finely tune the tool rotational speed by modulating the tool-bone interaction force along the same axis. The velocity control loop integrates also a bone layer transition detection algorithm that dynamically limits the tool velocity depending on the bone layer density. The approach was tested on the Kuka LWR4+ provided with an actuated surgical tapper which was used to tap a wood specimen simulating the bone layer density characteristics and bovine bones. A normalized maximum time delay in the bone layer transition detection of 0.25 was achieved by the experiments. A success rate of [Formula: see text] was achieved for all the tested tool velocities. The proposed control achieved a maximum steady-state error of 0.4 rpm. The study demonstrated high capability of the proposed approach to i) promptly detect transition among the specimen layers and ii) adapt the tool velocities depending on the detected layers.

Turning of Al 7075-T6 aerospace alloy under different sustainable metalworking fluid strategies by coated carbide tools

ABSTRACT We primarily need to reduce the consumption of metalworking fluid to ensure sustainable and eco-friendly machining of aerospace alloys. The present study was planned to determine the efficiency of various eco-friendly metalworking fluid strategies for the sustainable turning of aerospace aluminium alloy (Al7075-T6) coated carbide tools under different eco-friendly metalworking fluid strategies namely dry machining, minimum quantity lubrication (MQL), Ranque-Hilsch vortex tube (RHVT), and compressed air. Machining performance was investigated in terms of micro-hardness, tool tip temperature, tool wear, cutting forces, work surface roughness, chip morphology, and energy consumed. Results manifested that MQL and tool coatings can significantly lower tool tip temperature by up to 16%, tool wear by up to 102–106%, average cutting forces by 17–21%, and surface roughness reduced from 11–21% as compared to dry conditions. Abbreviations: BUE, built-up edge; CVD, chemical vapour deposition; CrN, chromium nitride; DCR, disposed chip ratio; DLC, diamond like carbon; DSPR, disposal scrap part ratio; EDS, energy dispersive X-ray spectroscopy; MF, metalworking fluid; MoS2, molybdenum disulphide; MQL minimum quantity lubrication; PVD, physical vapour deposition; RHVT, Ranque-hilsch vortex tube; RPSR, recycled part scrap ratio; RSPR, remanufacturing scrap part ratio; SEM, scanning electron microscopy; SDSS, super duplex stainless steel; TiAlN, titanium aluminium nitride

Study on the Influence of Tool Tip Radius on the Tooth Root Strength of Helical Cylindrical Gear

The bending fatigue strength of the tooth is an important index to measure the bearing capacity of the gear. The tooth root transition curve has a great influence on the bending strength of the gear. The profile of the tooth root transition curve depends on the shape of the tooltip. Therefore, the geometry of the tooltip must be considered in the simulation process of tooth profile generation. Contact analysis of helical gears with accurate geometric models is carried out in this paper. After generating tooth profiles machined by tools with different tip radii using MATLAB software, the three-dimensional model of involute helical cylindrical gears is established in CREO, and the stress distribution of gears under diverse load conditions is analyzed by FE software. In the end, it is concluded that the size of the tooltip fillet radius has a great influence on the maximum bending strength of the tooth root, and the strength of the tooth root decreases by increasing the tool tip radius.

Investigation of the cutting-edge radius size effect on dynamic forces in micro end milling of brass260

Rapid increases in the number of industries that need a sub-micron surface finish on 3D micro/meso technological innovation parts are being seen. Due to the high rotating speeds of activities, chatter behaviour also occurs during micro-cutting. Changes in bearing stiffness, gyroscopic effects, and misalignment are only some of the factors that need to be considered while studying the spindle's dynamics. By regulating the movement of the cutting edge, the cutting action may be made more consistent. The structure of the tools also affects the machine's dynamics. Since the modes of different machine-tool components interact with one another, the dynamics of the tool tip are affected. In this research, we consider a model of a micro spindle system to enhance machining accuracy. Timoshenko beam theory is used to account for shear deformation and rotational inertia effects due to the short and thick beam-type designs of each component of the micro tool. A detailed dynamical model of the moving micro end mill is created using an extended form of Hamilton's Principle. A two-degree-of-freedom model of the micro-milling process considers the modal dynamic properties of the tool-holder-spindle assembly and the micro-milling cutting forces. A three-dimensional finite element model of the system is built, and its dynamic response is gathered, to validate the full order finite element approach. Cutting force coefficients are then modelled as a function of instantaneous uncut chip thickness, which is principally affected by the tool edge radius and feed per tooth at different radial immersion depths.

Research on look ahead control of contour error for casting sand mold with five-axis linkage high speed machining

Casting sand mold with five-axis linkage high speed machining has the characteristics of high feeding speed, small milling force, fast tool axis swing speed and big contour error. The coupling relationships among tool axis swing, following error and contour error were analyzed, the computing method of axis movement speed for five-axis linkage machining was proposed, and a rapid linear estimation model of contour error for casting sand mold with five-axis linkage machining was established. On this basis, according to the relationships between rotary axis speed and tool axis swing speed, a look ahead self-adaptive control method of contour error for casting sand mold with five-axis linkage high speed machining was proposed, and an experiment of impeller sand mold with five-axis linkage machining was carried out. The results show that the contour error formed by tool tip can be estimated rapidly according to the tool axis swing speed in the process of casting sand mold with five-axis linkage high speed machining, and the proposed look ahead control of the rotary axis speed is an effective method for contour precision of casting sand mold with five-axis linkage high speed machining.

Global toolpath smoothing for CNC machining based on B-spline approximation with tool tip position adjustment

B-spline curve approximation is widely used for fitting linear toolpaths to improve machining quality and efficiency in CNC machining. For a high-quality smoothing method, the control of both approximation error and curve curvature needs to be taken into account. To reduce the maximum curve curvature while meeting the precision requirements, a B-spline approximation scheme with tool tip position adjustment is proposed in this paper. Toolpaths are first divided into several subdivisions according to the discrete curvature of each tool tip point. For subdivisions that need adjustment, tool tip positions are adjusted to minimize the maximum discrete curvature. An existing approximation method named energy-term-incorporated progressive and iterative approximation for least square fitting (ELSPIA) is selected and improved to fit the adjusted toolpaths and lower the chord errors. For improving the numerical stability of the ELSPIA method, the way of searching appropriate foot point parameters is discussed in this paper. Deviation expansion factors of tooltip points are also defined to make the ELSPIA method suitable for fitting the adjusted toolpaths. Both simulations and experimental studies are conducted to prove that the proposed method can significantly decrease the maximum curvature of fitted B-spline curves and improve the machining efficiency without exceeding the tolerance. For example, experimental results show that for the tested butterfly and rabbit toolpaths, the proposed method can improve the machining efficiency by 2.61% and 2.37%, compared with the ELSPIA method without tool tip position adjustment.

Effect of the inclined angle of micromilling tool on the fabrication of the microfluidic channel

Micromilling is a common processing method for fabricating microfluidic chips or other microproducts with high processing accuracy and low cost, which is suitable for mass production. The main concern of micromilling is the surface roughness of the work material. However, only a small range of surface roughness can be obtained in the general study of micromilling by changing the processing parameters, which is very difficult to obtain a specific roughness. In the process of micromilling with end mills, due to the structural characteristics of the tool tip, the inclination angle of the tool has a significant impact on the bottom surface of the machined channels. In this work, the influence of the tool inclination on the surface roughness was studied through the inclined micromilling tests of the poly(methyl methacrylate) (PMMA) surface, and it was proposed to realize the control of the machined surface roughness by inclined micromilling. In addition, a theoretical model considering tool inclination was established to calculate the surface roughness of the machined bottom obtained by inclined micromilling. The experimental results were consistent with the theoretical results under the low speeds. Afterwards, the polydimethylsiloxane (PDMS) was used to replicate the microchannel machined on the PMMA surface, and the microfluidic chips were prepared to control the fluid flow in the channel by adjusting the roughness of the bottom of the channel. Results indicated that the smoother channel flowed first under the same flow pressure. The study offers a new idea of surface roughness control, which can be applied to flow control in microfluidic chips.

Pre-compensation of contour errors for five-axis machine tools through constructing a model reference adaptive control

Existing contour error pre-compensation methods are sensitive to modeling errors during the prediction of contour errors. This article proposes an adaptive contour error pre-compensation method for five-axis machine tools. A model reference adaptive control (MRAC) for a feed drive system is constructed. Through transforming the control signals from the external proportional–proportional–integral (PPI) controller, MRAC makes the response of the real plant match that of the nominal model. Both feedback and feedforward laws are combined in the transformation. The transformation coefficients are updated in real time by the parameter adaption law. The model matching conditions are theoretically derived. Through model matching, the tool tip and tool orientation contour errors can be precisely predicted by the nominal model regardless of the modeling errors. Through utilizing the position Jacobian and the orientation Jacobian, the compensation signals are directly solved in the workpiece coordinate system (WCS) by the model predictive control (MPC) algorithm. Simulations and experiments show that the proposed method can obviously reduce the prediction errors and thus improve the contouring performances.

Modeling of heat partitioning and temperature rise at the tool-chip interface in diamond turning of the PBX surrogate

To predict the heat partition ratio and chip temperature rise in the diamond turning of a PBX surrogate, a comprehensive model is built in this work. The newly created model takes into account the removal and friction law of powder chips at the tool tip in addition to the diamond tool and important process parameters. The cutting heat generation and distribution rule are clearly outlined thanks to the successful integration of the momentum theorem (related to cutting force) and energy conservation theory (related to cutting heat). The following findings came from the high-speed face turning experiment based on simultaneous force-thermal monitoring: 1) The friction heat at the tool-chip interface is the primary cause of the temperature increase in the chip, and decreasing the heat partition ratio is advantageous for lowering the risk of thermochemical reactions of powder chips. 2) It is effective to suppress the proportion of heat obtained from powder chips by optimizing the diamond tool with a negative rake angle and reducing the equivalent cutting friction coefficient. 3) The most important aspect affecting the chip temperature rise is the cutting speed. Improving the tool-chip friction conditions and lowering the maximum cutting speed are essential for ensuring PBX machining safety.

Effects of tool angles and uncut chip thickness on consumption of plastic deformation energy during machining process

Research on the underlying mechanism that controls the chip deformation and energy consumption is a basis to instruct the cutting process planning and improve the machining efficiency. The metal cutting process can be treated as purposeful separation of workpiece material, and the stress state located at the tool tip has great effect on the fracture of material being removed. Through studying the relationship between the stress triaxiality and chip formation process, this paper aims to reveal the effects of tool rake angle, inclination angle and uncut chip thickness on chip deformation behavior and associated energy consumption during machining of 1045 steel based on finite element method (FEM). A two-dimensional FEM model for orthogonal cutting is developed to study the effect of tool rake angle and uncut chip thickness on chip deformation, while a three-dimensional FEM model for oblique cutting is developed to investigate the effect of tool inclination angle. The parameter of chip compression ratio (CCR) is adopted to assess the chip plastic deformation and energy consumption under varied machining conditions. The cutting force component calculated based on CCR is compared with the total cutting force to demonstrate the dominant role of chip plastic deformation in cutting energy consumption. The results indicate that larger rake angle and smaller inclination angle of cutting tools as well as larger uncut chip thickness lead to increase of stress triaxiality near the tool tip, which can reduce the material fracture strain and be beneficial for the separation of material being removed from the bulk workpiece. This paper will be attractive from both practical and fundamental perspectives devoted to instructing the optimization of cutting parameters to improve the processing efficiency and reduce the energy consumption.

Five-Axis Contour Error Control Based on Numerical Control Data

Improving contour accuracy is one of the significant goals of industrial machining. This paper proposes a contour error estimation and compensation algorithm for five-axis computer numerical control (CNC) machine tools based on modified numerical control (NC) codes. The expected path analyzed by NC data and the actual trajectory collected by sensors are spatially mapped by the hidden Markov model (HMM). Next, an evaluation function that hybrids the tool tip position and tool orientation change trend is proposed as the index of contour error estimation. Finally, spatial iterative learning control (ILC) is used to compensate the contour error, and high-precision machining instructions are obtained after multiple iterations. Experiments with different trajectories are performed on a five-axis platform to verify the proposed algorithm’s effectiveness. The results show that the proposed algorithm without using planned trajectories, has the same good control effect as traditional methods, which must know the planning trajectory for simple trajectories. At the same time, the method proposed in this paper has better performance than existing algorithms based on tool tip position nearest principle at sharp corners. In conclusion, on the basis of not depending on the planning trajectories, this method has a better compensation effect for the overall accuracy of trajectories and is easier to implement in industrial applications.

Experimental and modeling study of surface topography generation considering tool-workpiece vibration in high-precision turning

High-precision turning (HPT) is a main processing method for manufacturing rotary high-precision components, especially for metallic parts. However, the generated vibration between tool tip and workpiece during turning may seriously deteriorate the surface integrity. Therefore, exploring the effect of vibration on turning surface morphology and quality of copper parts using 3D surface topography regeneration model is crucial for predicting HPT performance. This developed model can update the machined surface topology in real time. In this study, the effects of tool arc radius, feed rate, radial vibration, axial vibration and tangential vibration on the surface topography and surface roughness were explored. The results show that the effect of radial vibration on surface topography is greater than that of axial vibration and tangential vibration. The radial vibration frequency is also critical. When vibration frequency changes, the surface topography profile presents three different types: the standard sinusoidal curve, the sinusoidal curve whose low-frequency signal envelopes high-frequency signal, and the oscillation curve whose low-frequency signal superimposes high-frequency signal. In addition, HPT experiment was carried out to validate the developed model. The surface roughness obtained in the experiment was Ra=53 nm, while the roughness obtained by the simulation was Ra = 46 nm, achieving a prediction accuracy of 86.7 %.Received 4 September 2022; revised 3 October 2022; accepted 17 October 2022.

A novel magnetorheological finishing process based on three revolving flat tip tools for external cylindrical surfaces

The magnetorheological finishing technique based on a stationary curved tip tool is found less effective in finishing external cylindrical surfaces. Therefore, three revolving flat tip tools-based magnetorheological finishing process which utilises the rotation of both workpiece and tools have been developed to address the issues of the existing method. Also, a feed mechanism has been built to provide the longitudinal movement to the workpiece. A workpiece of mild steel has been finished by both developed and existing methods. It has been observed that after finishing 1 hour 30 minutes with a stationary curved tip tool, surface roughness values Ra, Rq, and Rz decrease by 69.29%, 64.41%, and 61.26%, respectively. Whereas, the reduction in the surface roughness value of Ra, Rq, and Rz by 85.38%, 84.51%, and 82.7%, respectively, have been noted after finishing with the three revolving flat tip tools process at the same parameters and conditions.

Data-Driven Optimization for Deposition with Degradable Tools

We present a data-driven optimization approach for robotic controlled deposition with a degradable tool. Existing methods make the assumption that the tool tip is not changing or is replaced frequently. Errors can accumulate over time as the tool wears away and this leads to poor performance in the case where the tool degradation is unaccounted for during deposition. In the proposed approach, we utilize visual and force feedback to update the unknown model parameters of our tool-tip. Subsequently, we solve a constrained finite time optimal control problem for tracking a reference deposition profile, where our robot plans with the learned tool degradation dynamics. We focus on a robotic drawing problem as an illustrative example. Using real-world experiments, we show that the error in target vs actual deposition decreases when learned degradation models are used in the control design.

Minimum Quantity Lubrication (MQL) multiphase dynamics of a vibration-assisted drilling process

Metalworking fluid (MWF) consumption in machining processes can be minimised using minimum quantity lubrication (MQL). In the vibration-assisted drilling process, the MWF is transported as aerosol (dispersed droplets in gas) to the cutting zone through microchannels inside the drilling tool. Numerical simulations have been applied to elucidate the multiphase flow dynamics of the MWF inside a helical microchannel of a twist drilling tool. Numerical results indicate a transition from the inserted MQL aerosol flow and a wall film already after the first helical bend of the microchannel. The wall film contains > 90 % of the lubricant and is strongly localised on only 10 % of the microchannel circumference at the tool tip. This MQL-flow behaviour has to be considered in future investigations of the processes at the borehole ground, where even more complex phenomena occur.

Model based design of tuned mass dampers for boring bars of small diameter

Tuned mass dampers (TMD) are an established method to reduce self-excited chatter vibrations in turning. Regarding boring bars, the susceptibility to chatter increases with increasing length and, even more, with decreasing tool diameter.A novel TMD for boring bars with diameters down to 10mm is presented. The TMD-design, consisting of a mass and a spring-damper combination, is based on analytical and numerical modelling. By using a futed boring bar design, the available design space allows to place a damping mass of sufcient mass ratio at the tool tip. Cutting tests showed the reduction of vibrations.

Thermal necrosis-aided dental implant removal: A rabbit model pilot study.

The significant advances in the materials and biological aspects of dental implants haven't completely eradicated the implant failures. The removal of osseointegrated but otherwise failed implants present several challenges including adjacent tissues damage and necessity of bone augmentation for reimplantation. Controlled thermal necrosis has emerged as an alternative technique to aid removal of osseointegrated dental implants with minimal to no defect to healthy bone or surrounding tissues. This study aimed to evaluate the thermal necrosis-aided implant removal method in a rabbit osseointegration model. A total of 8 male New Zealand rabbits were used in the study. Two dental implants were placed on each femur of the rabbits. Heating of the implants was performed after 7 weeks following the implantation. Heating was done by contacting the tip of an electrosurgey tool in monopolar mode at different power settings and contact durations (5W - 2 seconds, 5W - 10 seconds, and 10 W - 10 seconds). No heating was done on the control group. Implant stability right after implantation, before heat application and after heat application was determined using an Osstell™ Mentor Device. Following the removal of implants histological analyses were performed to determine the effects of heat application at cellular level. ISQ values of the 10W-10s group was significantly lower compared to the other groups (p<0.001). No indication of progressive necrosis or irreversible damage was observed in any of the groups. However, the percent of empty-apoptotic lacunae were statistically higher in the 5W-10s and the 10W-10s groups compared the control and the 5W-2s groups. Within the conditions of this study, we conclude that heat application with an electrosurgery tool using monopolar mode at 10W power for 10 seconds is optimal for reversing osseointegration with no extensive or progressive damage to the bone.

Parameter optimization and microstructure evaluation of welding of structural steel 1020 and AA6062

AA6062 and ST1020 materials are used to perform friction stir spot welding (FSSW). In this experiment, the mechanical and microstructural characteristics of the welded joint were determined using a square-head tip tool. To enhance the life of the welded joint, three essential process parameters, namely tool speed, dwell time, and plunge depth were employed with four levels. The L16 orthogonal array was adapted for experimental work to develop a process parameter table. A tensile test was performed for a larger better value to predict the strength of the welded joint, and the value is 5.65 kN. The outcome shows that dwell time is a more prominent parameter than tool speed and plunge depth. The optimal combination of welding parameters is a dwell time of 24 s, a tool rotational speed of 1200 rpm, and a plunge depth of 0.8 mm; dwell time contributes 39.66%, followed by a plunge depth 35.7%, and at last, tool speed 6.171%. Furthermore, to determine the optimum level of parameters. The microstructure of this joint was observed with respect to heat dissipation and changes in grain size. Microstructure studies were carried out to see the area under stir zone for workpieces with high and low tensile strength. This work was validated using the response surface method (RSM). The RSM results are very close to the experimental results.

Taguchi Analysis of the Deformation Characteristics of Single-Point Cutting Tool with Micro-Tool Coatings During Orthogonal Machining

Machining, the art of processing materials, has progressed significantly over the past century. Advances in tool materials look at blended advantages of conventional and modern tool materials through coatings at micro-scales. Tool coatings improve the hot hardness and wear resistance of tool tip and faces. The current study utilizes the Taguchi technique to analyze the deformation response of HSS tools with three different tool coatings—titanium carbide, titanium nitride and titanium aluminum nitride. The coating thicknesses of 10, 50 and 100 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}m were employed on the rake face and the flank faces of the single-point cutting tool. The response of the tools while machining medium carbon steel 42CrMo4 has been studied using the finite element approach—transient structural analysis module on ANSYS®. The tool deformation was taken up as the key metric.

Fuzzy Logic Modelling Of The Effect Of Tool Tip Radius On Surface Roughness In Machining Co28Cr6Mo Wrought Steels In CNC Turning

This study includes fuzzy logic modeling of surface roughness experimental values obtained as a result of machining Co28Cr6Mo medical alloy in CNC turning (rotational speed (n), feed rate (f), depth of cut (a) and tool tip radius (r)) depending on cutting parameters. According to the hardness of the material to be cut and the type of cutting tool used, fuzzy logic solution models that can determine the most suitable tool tip radius for the surface roughness (Ra) were created. In the model created using fuzzy logic, experimental studies on the rule base created by using the membership functions of the input parameters and the output parameters, the membership function foot widths and the relations between the membership functions were used. Triangle (trimf) membership function was chosen with Mamdani approach on the rule base. The results obtained using the established model are interpreted with 2 and 3 dimensional graphics for tool tip radius. We can say that a good surface quality (minimum surface roughness) is obtained on the material with the most suitable (optimal) tool tip radius determined by models established with fuzzy logic.